Why I think the Satterlee and Audette Ladder Tests Work and Why-- You Decide!

[Veteran]

Does anyone have any idea what an average POI dispersal might be for quality barrels due to harmonics?

Harral in his work is looking at examples with .3 or .4 inches of dispersion for good groups and maybe double that for bad ones.

He shows this on MPC curves and by ladder test results with different barrel positions caused by harmonics.

But, I would not discount 2-3 inches of dispersion even at 100 yards depending on how bad the harmonics are what kind of
stiffness, and taper the specific barrel has and its weight, all of this against how powerful a load is being discharged in it.

Go here and dig down into his work, and you will get some insights on more normal cases.

Barrel Harmonics Are A Lot More Important Than You May Think or Know--Here's Proof

First, I have searched for information for about a year and half on this subject. Some of you may know of something really good I've missed, but the best source I have encountered for information on this topic is Al Harral. Who is Al Harral? Al Harral is a retired guy--but one smart...

www.longrangehunting.com

 

[Peter Van Dyke]

Thank you. My interest in this stems from a recent experience after rebarreling my primary rifle with a SS 26" Bartlein heavy varmint barrel. The range that day was busy. We had to shoot at the 50yard range. The first cartridges sent through it were match grade. The five shot group was disappointing. We then used cartridges I had built for another rifle with a 22" carbon Proof Research barrel. This 5 shot group was very good. This experience caused me to think about how cartridges built for a very different barrel could be so good. My luck in life thus far has not been that good. I don't think it was merely luck that the cartridges I built for one rifle would shoot so well in an unknown and very different barrel. I am now reconsidering how I develop a load. The imperial evidence I have gathered throughout my loading career suggests overwhelmingly that the care with which I make a cartridge has substantially more impact on POI consistency than any other factor, other than shooting technique of course.

 

[Veteran]

Thank you. My interest in this stems from a recent experience after rebarreling my primary rifle with a SS 26" Bartlein heavy varmint barrel. The range that day was busy. We had to shoot at the 50yard range. The first cartridges sent through it were match grade. The five shot group was disappointing. We then used cartridges I had built for another rifle with a 22" carbon Proof Research barrel. This 5 shot group was very good. This experience caused me to think about how cartridges built for a very different barrel could be so good. My luck in life thus far has not been that good. I don't think it was merely luck that the cartridges I built for one rifle would shoot so well in an unknown and very different barrel. I am now reconsidering how I develop a load. The imperial evidence I have gathered throughout my loading career suggests overwhelmingly that the care with which I make a cartridge has substantially more impact on POI consistency than any other factor, other than shooting technique of course.

Different ammo, different powder w diiferent burn rate Ba, different burn rate pressure curves, therefore different velocities, different bullet time to exit bbl. Different timing to exit bbl, different direction bbl is pointing due to harmonics.

It would be interesting if you had velocities and powder types, bullet types, and seating depths on both bbls. w both sets of ammo.

But yes, Im sure quiet different harmonics and grouping results.

Did you also notice any change in POI clusters of groups with different ammo?

 

[Peter Van Dyke]

I keep pretty thorough records. I have those numbers and can provide them. But my current interest is hypothetical. My recent shift in hand loading perspective revolves around my deep need to consider constants and variables when looking for a superior way to build a cartridge. When I remove cartridge variability by stipulating perfect cartridges, hypothetically of course, I then consider remaining constants and variables. So all the variables pertaining to the cartridge are no longer in play. When firing mechanisms, chamber quality, bore quality, muzzle quality, integrity of the rifle system, etc. are stable we further shorten the list of variables. We are left with external ballistics and shooting technique. So let's stipulate that these too are constant. Let's go back the the perfect cartridge. Let's say I seat bullets deeper in an amount that shifts POI. Let's say I have created 5 such cartridges. My current loading perspective informs me that those 5 cartridges should produce the same POI, if say, barrel harmonics or any other modified constants indeed are constant. If not why not?

 

[Peter Van Dyke]

I think that I should point out that I am not interested in shifting any body's views on hand loading. I'm simply curious if my musings are valid.

 

[WildRose]

Does anyone have any idea what an average POI dispersal might be for quality barrels due to harmonics?

Honestly I don't think there is any way to definitely know since literally everything that touches the barreled action can affect the harmonics.

You can get a fair idea by doing before and after groups with a new rifle that you buy and then have to float and bed or rework the bedding on.

Even something as minor as slight variations of the torque on mounting screws from spec is going to have some effect.

The biggest problem is that you can't really eliminate all of the other possible contributors that cause dispersal reasonably so it would take a very well designed and expensive series of experiments to narrow it down enough to even form a good hypothesis much less to thoroughly test it.

 

[WildRose]

I keep pretty thorough records. I have those numbers and can provide them. But my current interest is hypothetical. My recent shift in hand loading perspective revolves around my deep need to consider constants and variables when looking for a superior way to build a cartridge. When I remove cartridge variability by stipulating perfect cartridges, hypothetically of course, I then consider remaining constants and variables. So all the variables pertaining to the cartridge are no longer in play. When firing mechanisms, chamber quality, bore quality, muzzle quality, integrity of the rifle system, etc. are stable we further shorten the list of variables. We are left with external ballistics and shooting technique. So let's stipulate that these too are constant. Let's go back the the perfect cartridge. Let's say I seat bullets deeper in an amount that shifts POI. Let's say I have created 5 such cartridges. My current loading perspective informs me that those 5 cartridges should produce the same POI, if say, barrel harmonics or any other modified constants indeed are constant. If not why not?

Theoretically with all things being equal you could test it. The trouble is designing a test then where you could properly gather enough data to know for sure. You'd need a very large sample size to really get good data and creating those perfect conditions for each shot is just not something easily or practically done.

 

[Veteran]

Theoretically with all things being equal you could test it. The trouble is designing a test then where you could properly gather enough data to know for sure. You'd need a very large sample size to really get good data and creating those perfect conditions for each shot is just not something easily or practically done.

Thats why Haral built a finite element model, which has a barrel with an almost infinite number of cells (you can tell the model to make millions of cells and time steps as it calculates the pressures, sound waves, frequencies, friction, etc. cell to cell as the bullet goes down the barrel), and you can repeat the experiment as many times as you want and never change the answer unless you change the model inputs.

Im sure he trued his model or history matched it to actual data to start with.

This is the same way, Oil companies study and predict fluid flow through porous media, ie rock, its the same way we model rocket ballistics and flight, and the same way engineers fugure out structural loads and deformation and materials failure problems. They build very detailed cell to cell models which calculate events from a starting point and endpoint at one cell becomes the start point of the next cell and at the end of the model, one gets a resulting set of final conditions.

 

[Peter Van Dyke]

I've been lurking this forum for maybe fifteen years. When I was a kid I had some amazing experiences hunting with my father in Argentina and California. The hunting we did in Argentina was was wasted perhaps on a 10 year old kid at the time. Youth truly is wasted on the young. Nearly as amazing as our experiences in Argentina were I also used to walk from our home in California across the UC Berkeley campus near South Gate to a shooting range under Harmon Gym near South Gate carrying a .22 bolt action rifle over my shoulder several; times a week. I'd like to try that today. At that time shooting was easy. That to say that I hit what I was aiming at with ease. I quit shooting. I probably discovered girls or some such. Over fifty years passed before I started shooting again. My son became interested in shooting and watching him brought back fond memories. I had never shot a hand gun before. He and I went to a local shop and I bought a 1911 45 auto. I brought it home got a cardboard box and went down to the pasture with gun and box. I put the box on the ground paced off thirty paces. I couldn't hit that box to save my sole. I found this disillusioning. I consulted friends who shoot and it was suggested I get closer to the box. Thus began my renewed interest in shooting. My goal since then has been to hit what I am aiming at. I had no knowledge of hand loading. I was not aware such a thing was possible. I was raised under a roof where scientific methodology ruled. Trouble ensued were it discovered we might have designed or executed an experiment sloppily. Hand loading was utterly new to me. I brought little baggage with me. My approach from the beginning has been to fashion a cartridge perfectly (or at least consistently). This has turned out to be no easy task. My rudimentary understanding of the physics of internal ballistics coupled with my fixation on constants and variables toward discovering a way to hand load without depending on the forgiveness of sweet spots. My progress toward that goal gives pleasure and hope that I might get close enough to give me satisfaction. While I understand the value of seeking sweet spots, plateaus, nodes and the like, I will employ them when I run out of options. This my own personal rabbit hole. I don't recommend it to anyone. I am enjoying the journey. When I saw this thread I though I would enlist this venerable group to disabuse me my self constraining restrictions. I have never shot a ladder test or seating depth test. I am too stingy with components. Particularly during these dark times, I can shoot only to 200 yards at home. I also shoot 700 yards at a secret place in the woods locally. At 200 yards I regularly shoot 0.05 MOA and rarely over 0.75 MOA. However I'm focusing on vertical stringing over horizontal stringing at this time. So my MOA numbers reference vertical stringing only. I always put the crosshairs on my aim point and don't hold or dial. I saw a marked improvement in my groups after cataract surgery on my dominant eye. Go figure.

 

[WildRose]

Thats why Haral built a finite element model, which has a barrel with an almost infinite number of cells (you can tell the model to make millions of cells and time steps as it calculates the pressures, sound waves, frequencies, friction, etc. cell to cell as the bullet goes down the barrel), and you can repeat the experiment as many times as you want and never change the answer unless you change the model inputs.

Im sure he trued his model or history matched it to actual data to start with.

This is the same way, Oil companies study and predict fluid flow through porous media, ie rock, its the same way we model rocket ballistics and flight, and the same way engineers fugure out structural loads and deformation and materials failure problems. They build very detailed cell to cell models which calculate events from a starting point and endpoint at one cell becomes the start point of the next cell and at the end of the model, one gets a resulting set of final conditions.

All true, but those harmonics are going to vary greatly from barrel to barrel, contour and finish to contour and finish.
He essentially created a static model that produces consistent and predicable results for that particular barrel but the validity of the experiment is limited to that barrel and those like it.

 

[Veteran]

All true, but those harmonics are going to vary greatly from barrel to barrel, contour and finish to contour and finish.
He essentially created a static model that produces consistent and predicable results for that particular barrel but the validity of the experiment is limited to that barrel and those like it.

Yes, very true. Every rifle bbl and taper stiffness and weight are all different. We have to go shoot and tune using the emperical data from the rig we brung to the dance.

 

[WildRose]

Yes, very true. Every rifle bbl and taper stiffness and weight are all different. We have to go shoot and tune using the emperical data from the rig we brung to the dance.

It's like, "how to please the wife".

There are as many correct answer as their are successful marriages.

 

[Maol]

Below is a link to a interesting magazine article. It's a good intro and history to a experiment some here I suspect already know of. I found it found it illuminating, most will enjoy it at least.

The Houston Warehouse Experiment

What happened to the Rifle w/Pics is the 2nd Post Here

 

[aschler]

Different ammo, different powder w diiferent burn rate Ba, different burn rate pressure curves, therefore different velocities, different bullet time to exit bbl. Different timing to exit bbl, different direction bbl is pointing due to harmonics.

It would be interesting if you had velocities and powder types, bullet types, and seating depths on both bbls. w both sets of ammo.

But yes, Im sure quiet different harmonics and grouping results.

Did you also notice any change in POI clusters of groups with different ammo?

I have quite a few ARs in 223 Wylde or 5.56 Nato; the barrels are 11", 14.5", 16", 18", 20" and 24". I've been suprised how close the charge weights for a good node are between all these barrels, never more than a few tenths of a grain apart. Obviously the velocities are vastly different as well as the groups but the charge weights seems to carry over pretty well.